Vehicle powertrains may include transmissions to transfer power and torque from an engine to the vehicle output (axles or wheels). Hybrid powertrains may include multiple primary movers, including internal combustion engines or alternative power sources, such as one or more electric machines coupled with an energy storage device. When the powertrain is equipped with an additional primary mover, such as an electric machine, the transmission may also transfer torque and power from the electric machine to provide traction for the vehicle. Fixed-gears or speed ratios allow the engine to operate within a narrow range of speeds while providing a wide range of output speeds to the powertrain.
Vehicles having either conventional internal combustion or hybrid gasoline/electric transmissions typically utilize a plurality of gear sets and a plurality of torque-transmitting devices know as clutches, which may include a selectable one-way clutch (SOWC) as one of the clutches. The gear sets and clutches, including the SOWC can be selectively engaged and disengaged alone or in various combinations to provide powertrain functionality. The SOWC is a torque transfer mechanism that is capable of producing a mechanical connection between a driving member of the transmission via a rotatable input race or a first coupling plate of the SOWC, and an independent driven member of the transmission via an output race or second coupling plate of the SOWC, in one or both rotational directions. A SOWC may overrun in one or both directions of rotation depending on its particular design. Typically, a SOWC contains a selector device, such as a selection ring or slide plate, the movement of which selects the operating mode of the SOWC. A control plunger or selection lever may be used to move the selection ring. The selection lever may be actuated by one or more hydraulic components, which may include a piston or other hydraulic actuator controlled by one or more valves linked to the hydraulic components. The hydraulic pressure regulated or provided by these valves actuates the movement of the selection lever and selection ring to actuate the selected SOWC operating mode.